The compound telmisartan is known from European Patent EP 502 314 B1 (corresponding to U.S. Pat. No. 5,591,762, which is hereby incorporated by reference) and has the following chemical structure:

Telmisartan, and the physiologically acceptable salts thereof, have valuable pharmacological properties. Telmisartan is an angiotensin antagonist, particularly an angiotensin II antagonist which, by virtue of its pharmacological properties, may be used, for example, to treat hypertension and cardiac insufficiency, to treat ischemic peripheral circulatory disorders and myocardial ischaemia (angina), to prevent the progression of cardiac insufficiency after myocardial infarct, and to treat diabetic neuropathy, glaucoma, gastrointestinal diseases and bladder diseases. Other possible therapeutic applications can be found in EP 502 314 B1 and WO 02/15891, the contents of which are hereby referred to.
Hydrochlorothiazide (HCTZ) is a thiazide diuretic which is taken orally to treat edema and high blood pressure. The chemical name of HCTZ is 6-chloro-3,4-dihydro-2H-1,2,4-benzothiadiazin-7-sulfonamide-1,1-dioxide and the compound has the following structural formula:

Telmisartan is commercially obtainable under the trademark MICARDIS®, while a combination of telmisartan with hydrochlorothiazide (HCTZ) is commercially obtainable under the trademark MICARDIS® HCT (MICARDIS PLUS in Europe). Starting from the free acid of telmisartan, these formulations are produced by a complex spray drying process. Because of the limited solubility of the free acid, less complex methods of preparing an alternative preparation are difficult to achieve.
The aim of the present invention is to provide telmisartan in a form which enables a formulation of this active substance to be prepared in a less complex form. It has to be borne in mind that generally the production of a composition containing a pharmaceutically active substance is dependent on various parameters which are linked to the nature of the active ingredient itself. Without being tied thereto, examples of these parameters are the stability of effect of the starting material under different environmental conditions, the stability during the manufacture of the pharmaceutical formulation, and the stability in the final compositions of the pharmaceutical preparation. The pharmaceutically active substance used to prepare the abovementioned pharmaceutical composition should be as pure as possible. At the same time, its stability on long-term storage must be guaranteed under various environmental conditions. This is absolutely essential, in order to prevent pharmaceutical compositions being used which contain, in addition to the active substance proper, breakdown products thereof. In such a case, the actual content of active substance present in a preparation produced therefrom may be less than the specified amount.
Another aspect which is important in the production of solid preparations is that the active substance should have the most stable possible crystalline morphology for the pharmaceutical quality of a medicinal formulation. If this is not the case, the morphology of the active substance may change in certain circumstances under the conditions of manufacture of the preparation. Such a change may in turn affect the reproducibility of the manufacturing process and thus lead to final formulations which do not meet the high quality requirements imposed on pharmaceutical formulations. To this extent it should generally be borne in mind that any change to the solid state of a pharmaceutical composition which can improve its physical and chemical stability gives a significant advantage over less stable forms of the same drug.
The object of the invention is thus to provide a new pharmaceutical composition containing a stable form of telmisartan which complies with the abovementioned stringent requirements imposed on a pharmaceutically active substance.